To start...I know essentially nothing about RV furnances.
Here's some contact info (if it's a Suburban...):
NOTE: Our service technicians are available to assist you in making repairs or parts replacements from 8:00 a.m. to 5:00 p.m. Eastern Standard Time, Monday through Friday (except holidays), by calling 423-775-2131 extension 7102. E-mail address: email@example.com
In looking through my Suburban manual (I've got a SF-30FQ) it sure looks like the same motor drives both the combustion gas intake/exhaust and the heated air circulator:
The power then flows to the motor and allows the blower to operate. One end of the motor shaft drives the room air wheel. The other end of the motor shaft drives the combustion air wheel that delivers the required air to the burner for combustion.
So it seems like if you've got one, you should have both, unless there's some sort of mechanical failure of the "motor shaft" assembly.